Vm. Miller et Pm. Vanhoutte, Prostaglandins but not nitric oxide are endothelium-derived relaxing factors in the trout aorta, ACT PHAR SI, 21(10), 2000, pp. 871-876
yAIM: To identify the type of prostanoids produced by endothelial cells of
trout aorta and to determine whether or not the smooth muscle responds to n
itric oxide. METHODS: Ventral aortas, with and without endothelium from rai
nbow trout (S gairdneri), were incubated in a buffered salt solution. RESUL
TS: Addition of the calcium ionophore A23187 caused a significant increase
in prostaglandin E's and a consistent increase in the stable metabolite of
prostacyclin (6-keto-prostaglandin F-1 alpha) in the incubation media only
when the endothelium was present. This production was inhibited by methylen
e blue (10 mu mol/L). In rings of trout aorta without endothelium suspended
for the measurement of isometric force in organ chambers, prostacyclin and
prostaglandin E-1 but not prostaglandin E-2 caused concentration-dependent
decreases in tension when the rings were contracted with acetylcholine. Th
e smooth muscle did not relax to nitric oxide but did so to sodium nitropru
sside. Relaxations to the latter nitrovasodilator were not inhibited by met
hylene blue. Descending aorta without endothelium from frogs relaxed in a c
oncentration-dependent manner to nitric oxide. CONCLUSION: Predominant endo
thelium-derived relaxing factors in trout aorta are prostaglandins, the syn
thesis of which can be inhibited by methylene blue. A phylogenetic appearan
ce of nitric-oxide sensitive mechanism for vasodilatation, perhaps is assoc
iated with the transition from water to air respiration.